Apparatus for continuously freeze-drying granulates

ABSTRACT

A freeze-drying apparatus includes a vacuum chamber, and a drying bed arranged within the vacuum chamber, which drying bed has the shape of a helix disposed about a vertical axis. Means are provided for supplying the frozen particles at one end of the drying bed, for moving the frozen particles along the drying bed, for retaining the particles on the bed while they are being moved, and for removing the particles from the other end of the drying bed. Means are also supplied which heat the frozen particles while they are being moved along the bed so as to aid sublimation.

United States Patent Inventors Georg-Wilhelm Oetjen Cologne Marienburg;

l-lanns Eilenberg, Rosrath, Germany 819,305

Apr. 25, 1969 Appl. No. Filed Patented Apr. 13, 1971 Assignee Leybold-Heraeus-Verwaltungs-GmbH Cologne-Bayental, Germany Priority Apr. 25, 1968 Germany APPARATUS FOR CONTINUOUSLY FREEZE- 24 PRODUCT INLET W 8" FIRST COOLED HOPPER GATE VALVE PRODUCT VIBRATING DISPENSER LOWEST HELICAL BED m vAcuuu PUMP PRODUC OUTL ET Primary Examiner-William J. Wye Attorney-Spencer & Kaye ABSTRACT: A freeze-drying apparatus includes a vacuum chamber, and a drying bed arranged within the vacuum chamber, which drying bed has the shape of a helix disposed about a vertical axis. Means are provided for supplying the frozen particles at one end of the drying bed, for moving the frozen particles along the drying bed, for retaining the particles on the bed while they are being moved, and for removing the particles from the other end of the drying bed. Means are also supplied which heat the frozen particles while they are being moved along the bed so as to aid sublimation CONDENSER AND vacuum PUMP PARTICLE MOVING AND HEATING BED PARTICLES DRIED FALLING DOWN Patented April 13, 1971 3,574,951

4 Slants-Shoat 1 FIRST COOLED HOPPER CONDENSER AND VACUUM PUMP PRODUCT I PARTIcLE MOVING I AND HEATING BED INNER E HOPPER VIBRATING [DISPENSER I LOWEST I HELICAL BED II I" ;',I PARTICLES DRIED I FALLING DOWN X"? GATE VALVE vAcuuNI PUMP DISCHARGE LOCK GATE VALVE F I G l PRODUCT OUTLETJ INVENTORS Georg-Wilhelm Oeijen 8I Hcmns Eilenberg ATTORNEY-9 Patented A ril 13, 1911 I ,574,951

4 Sheets-Shoot 2 IN VE N TORS Georg-Wilhelm Oetjen 8:

Honns Ellenberg ATTORNEYS Patented A ril 13, 1911 I 3,574,951

4 Shoots-Shoot 5 INVENTORS Georg wilhelm Oetjen 8| Harms Eilenberg ATTORNEYS Patented A ril 13, 1971 4 Sheets-Shoot 4 I 'FIG.6.

SPIRAL 1:3 \:3

MICROWAVE HEATER FIG.7.

F I INVENTORS Georg-Wilhelm Oetjen 8 Hanns Eilenberg W? 7% ATTORNEYS APPARATUS FOR CONTINUOUSLY FREEZE-DRYING GRANULATES BACKGROUND OF THE INVENTION This invention relates to freeze-drying apparatus, and particularly to such an apparatus in which frozen granulates are continuously moved through the freeze-drying apparatus on a helical drying bed.

Continuous freeze-drying devices are known in which frozen granulates which have previously been comminuted to a suitable size are continuously brought into a vacuum drying chamber through a lock device, and are dried while being moved on a heated. drying bed. Dried granulates are continuously discharged from the vacuum drying chamber through vacuum locks. Vibratory drives are quite often used to convey the particles along the drying beds within the vacuum chamber.

Some of the known devices operate with a succession of vibratory drying beds disposed in the vacuum drying chamber. the material to be dried falling forma higher disposed bed onto a second drying bed which isdisposed somewhat below the first drying bed and extends in the same conveying direction. The material to be dried falls from the end of the first or higher bed onto the beginning of the second drying bed, and in the same fashion falls onto other drying beds. In this manner the desired degree of dryness of the granulates is achieved by the time the particles reach the end of the drying chamber. Other drying devices are provided in which the vibratory drying beds are disposed one on top of the other and in which the material to be dried traverses the first drying bed in a first direction, then falls ontothe second drying bed which carries it in the opposite direction falls onto a third bed which carries it in the original direction and so on.

Although the drying process in the above devices is accomplished in a satisfactory fashion, they are complicated in construction and require a substantial amount of space, which results in increased production costs. A further drawback is that this type of apparatus normally provides a good drying result only if the frozen particles all have the same grain size. This grain size must be predetermined as exactly as possible. Particles which are larger or smaller than this average size must be sorted out before entry into the vacuum drying chamber and are subjected to special treatment.

Among the objects of the present invention is the provision of a continuous freezedrying apparatus which is able to process granulates of frozen material which are of a different size.

Another object of the present invention is to provide a continuous freeze-drying apparatus which can process a relatively large amount of material in a relatively compact space.

Briefly stated, the objects of the present invention are achieved by providing a helical drying bed having a vertical axis which is arranged within a vacuum chamber. The helical drying bed includes means for conveying the frozen particles to be dried along the drying bed, and means at each side of the conveying surface for maintaining the articles on the surface.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of the apparatus in which the present invention is used.

FIG. 2 is a sectional view of one embodiment of the present invention.

FIG. 3 is a perspective view of the vibrating drive.

FIG. 4 is a sectional view of the vibrating drive.

FIG. 5 is a sectional view of another embodiment of the present invention.

FIG. 6 is a sectional view of still another embodiment of the invention.

FIG. 7 is a fragmentary sectional view of a variation of the fonn of the invention according to FIG. 6.

FIG. 8 is a sectional view of the drying bed of FIG. 2 wherein microwave heating is used.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. I discloses apparatus with which the present invention is to be utilized. A first cooled hopper 10 is provided which is filled with the frozen granular material. From this hopper, the material is introduced into a vacuum chamber 12 to an inner hopper 14 from which the material passes onto a vibrating dispenser l6 and to helical drying bed 18, which is the basic part of the present invention. The dried particles pass from helical dryer 18 to a discharge lock 20.

At the start of the operation the product inlet 22 is opened and the product is introduced into the first cooled hopper 10. When a sufficient amount of material has been introduced, the product inlet 22 is sealed and, via opening 24, which is connected to vacuum producing apparatus, such as a vacuum pump, a vacuum is produced in the first cooled hopper 10. When the vacuum in the first cooled hopper I0 is the same as that of the drying chamber 12, the gate valve 26 is opened and at about the same time the stirrer 28 is again moved (it is also moved as hopper 10 is being filled) so that the granular material which is frozen will pass through the gate valve 26 which has been opened and into the inner hopper 14 inside chamber 12. The granular material is then moved along vibrating dispenser 16 to the lowest end of the helical bed 18. The material travels up the helical bed to the top and then falls down through a central opening. By the time the particles are falling, they have been fully dried, and the material may be collected in a collecting hopper 30 which is also inside the vacuum chamber 12. When a sufficient amount of material has been collected in collecting hopper 30, the discharge lock 20 via vacuum connection 32, which is connected to a vacuum pump, is evacuated. During this time, the gate valve 34 between hopper 30 and discharge lock 20 is closed as is gate valve 36 which is the product outlet. After the vacuum in the discharge lock 20 is the same as that in vacuum chamber 12, gate valve 34 is opened and the material passes into the discharge lock 20. When a sufficient amount of material has passed into the discharge lock, the gate valve 34 is closed and gate valve 36 is opened at which time the discharge lock 20 is vented and the vacuum is lost, and at the same time the product discharges from the outlet valve 36.

The vacuum chamber 12 is provided with outlet 38 which is connected to a vacuum pump to maintain a vacuum in chamber 12 as well as to a surface condenser.

With more particular reference to FIG. 2, one embodiment of helical drying bed is disclosed which includes a hollow cylinder 40 at whose outer periphery a .irying bed 42 is arranged.

The cylindrical wall 44 of the hollow cylinder 40 serves as a retaining abutment on one side of the helical drying bed, and a raised flange 46 at the outer edge of the helical bed serves as a wall for retaining articles on the other side of the bed. A vibratory drive mechanism 48 is arranged to move cylinder 40 and the drying bed 42 through a small angle with quick movements in order to move particles upwardly on the bed. Particles to be frozen are delivered to the lower end 50 of the drying bed, are conveyed therealong to upper end 52 of the bed and are then delivered to an opening 54 formed by a funnel-shaped member 56 having its upper end joined to the upper end of cylinder 40 and a circular opening 58 at its bottom. A central cylinder 60 which is coaxial with cylinder 40 has its upper end joined to the lower end of funnel-shaped member 56 and its lower end 62 arranged to deliver material to the outlet vacuum lock 20. The details of the vibratory drive mechanism 48 are shown in further detail in FIGS. 3 and 4. The drive mechanism includes a lower fixed plate 51 having a central opening 53 therein through which the lower end 62 of inner cylinder 60 (See FIG. 2) may pass. Art upper plate is provided which also has an opening 57 for the same purpose. Leaf springs 59 which are inclined as shown are provided to connect plates 51 and 55 together. An electromagnet 61 is fastened to the stationary baseplate 51 and an armature or electrical yoke 63 is fastened to the upper plate 55. If the coils of electromagnet 61 are connected to a conventional AC source (50 cycles in Europe and 60 cycles in the United States), the vibrating action will be 50 or 60 cycles per second. In the embodiment shown, when the electromagnet 61 is energized, the plate 55 will move downwardly and, looking from the top, clockwise, whereas when the electromagnet is deenergized, the plate 55 will move upwardly and counterclockwise.

FIG. discloses another embodiment of the invention in which a drying bed 64 is disposed at the outer periphery of hollow cylinder 65. An additional drying bed 66 is disposed along the inner periphery of cylinder 65. An inner retaining flange 67 is disposed on the inner edge of helical drying bed 66.

A continuous opening 68 passes through the center of hollow cylinder 65, its periphery being defined in part by the flanges 67. Opening 68 serves as a conduit for the removal of vapor components discharged from the material to be dried.

The upper end 69 of the outer conveyor 64 is displaced radially inward so as to conduct the material to the inner helical drying bed 66. In operation, articles to be frozen are delivered to the lower end 70 of drying bed 64, are carried to the upper end 69 and are moved radially inward to the upper end '71 of inner drying bed 66. The particles are conveyed downwardly to the lower end 72 of bed 66 and are then moved out of the vacuum chamber in a manner generally the same as in the FIG. 2 embodiment.

FIG. 6 discloses still another embodiment of the invention which is generally similar to that of FIG. 2 except that a second hollow cylinder 73 is concentrically disposed within cylinder 74. Cylinder 73 has a helical drying bed 75 disposed about its outer periphery. A cylinder 76 for removal of dried material from the outer conveyor bed 77 is arranged between the inner drying bed 75 and the wall 78 of cylinder 74. A cylinder 79 for removal of articles dried on the inner drying bed 75 is arranged concentrically within cylinder 73, and has a structure generally similar to that of the cylinder 62 of the FIG. 2 embodiment.

Inner drying bed 75 and outer drying bed 77 are formed with different slopes relative to the horizontal.

Separate vibratory drive mechanisms 80 and 81 are arranged to drive the outer drying bed 77 and the inner drying bed 75 at different angular speeds. If the drying beds were moved at the same angular speed, the granulate would pass through at the same speed.

By virtue of their different slopes and their differing vibratory movement speeds, inner drying bed 75 and outer bed 77 may be adjusted to dry particles at different rates. This permits drying of particles of different sizes in the same apparatus.

FIG. 7 discloses a variation of the FIG. 6 apparatus. The drying bed 77 has a region between cylinder 74 and the outer flange 82 subdivided into three conveying beds 77a, 77b and 770 by rib-shaped vertical walls 83 and 84 secured to the conveying surface. A similar subdivision may be made of the inner conveyor 75.

By virtue of their different radial lengths each of the conveyors 77a, 77b, 770 have different lengths and particles travel different distances on each conveyor.

As can be seen in FIG. 7, the bottom of the bed comprises a double-walled heat jacket 85, and a flexible hose 86 is connected to communicate with this jacket so that heat, for example in the form of steam or the like, can be moved into and through the double-walledjacket. Not only the bed shown in FIG. 7, but also the beds in all of the previous embodiments can have double-walled jackets with flexible hoses connected thereto forming the steam inlets and steam outlets so that the beds will be heated. If desired, the beds of FIG. 6 can he provided with different amounts of heat.

Also, if desired, a different amount of heat can be supplied to the inner helical drying bed of FIG. 5 than is supplied to the outer helical bed. The inner part ofthe drying device may then be used exclusively for supplemental drying.

The use of such inner drying arrangements makes an advantageous use of the central region of the cylinder which has been evacuated at high expense by the vacuum apparatus.

The provision of a separate vibratory drive mechanism for the inner cylinders, and a provision of a different angular slope permits design and operational variations so that particles may stay in the different regions for different periods of time. In this way the drying characteristics may be different in different regions, and accordingly a wider range of sizes of frozen particles may be advantageously dried.

As shown in FIG. 8, a further device is provided which is very similar to that of FIG. 2. However, instead of using the double-walled jackets which would otherwise be used with the FIGS. 2, 5, 6 and 7 embodiments, a microwave heating arrangement is provided. The same elements of FIGS. 8 and 2 are provided with identical reference numerals. However, a microwave heater in the form of a helical device which is disposed slightly above the bed is provided. In this arrangement, the damp particles are heated whereas the already dried particles are not influenced by this type of heat and this minimizes the danger of excess drying of the particles. While it is realized that there will be some heating of the bed itself, the direct heating from the microwave source to the particles is lessened for those particles which have already been fully dried.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations.

We claim:

I. A freeze-drying apparatus comprising:

a. a vacuum chamber having inlet vacuum lock means for delivery of frozen particles into its interior without subjecting the interior of the chamber to atmospheric pressure;

b. a hollow cylinder arranged in vertical position within the vacuum chamber having a drying bed in the shape of a helix disposed about its outer periphery;

0. means for supplying said frozen particles from the inlet lock means to one end of the drying bed;

d. means connnected to the drying bed for imparting motion thereto and for moving frozen particles there along;

e. abutment means on the side of the drying bed opposite said cylinder for retaining said particles on the bed while they are being moved;

. means for heating said particles while they are being moved along the bed; and

g. outlet vacuum lock means on the vacuum chamber for removing said particles from the chamber upon completion of the drying process without subjecting the interior of the chamber to atmospheric pressure.

2. The combination defined in claim 1 including means for removing the particles from the upper end of the drying bed to an opening at the end of said cylinder, said outlet vacuum lock means being located below said cylinder.

3. The combination as defined in claim 1 wherein said motion imparting means and said drying bed are arranged to move the particles in an upward direction along said bed.

4. The combination defined in claim 3 wherein said helical drying bed is located on the outer periphery of said cylinder and an additional helical drying bed is located on the inner periphery of said cylinder, said inner helical drying bed and said motion imparting means being arranged to move the particles in a downward direction along said inner bed, said beds being arranged to move in the same direction.

5. The combination defined in claim 1 including a plurality of hollow cylinders, each having a different diameter, and each having a helical drying bed connected to its periphery, said cylinders and their associated drying beds being concentric and arranged within said vacuum chamber, and separate means for imparting motion to each of said helical drying beds.

6. The combination defined in claim 4 wherein each of said helical drying beds has a different slope.

drying bed;

d. means for moving the frozen particles along the drying bed;

e. means on each side of the drying bed for retaining the particles on the bed while they are being moved;

f. means for heating the frozen particles while they are being moved along the bed; and

g. means for removing the particles from the other end of the drying bed. 

2. The combination defined in claim 1 includiNg means for removing the particles from the upper end of the drying bed to an opening at the end of said cylinder, said outlet vacuum lock means being located below said cylinder.
 3. The combination as defined in claim 1 wherein said motion imparting means and said drying bed are arranged to move the particles in an upward direction along said bed.
 4. The combination defined in claim 3 wherein said helical drying bed is located on the outer periphery of said cylinder and an additional helical drying bed is located on the inner periphery of said cylinder, said inner helical drying bed and said motion imparting means being arranged to move the particles in a downward direction along said inner bed, said beds being arranged to move in the same direction.
 5. The combination defined in claim 1 including a plurality of hollow cylinders, each having a different diameter, and each having a helical drying bed connected to its periphery, said cylinders and their associated drying beds being concentric and arranged within said vacuum chamber, and separate means for imparting motion to each of said helical drying beds.
 6. The combination defined in claim 4 wherein each of said helical drying beds has a different slope.
 7. The combination defined in claim 5 including rib-shaped dividing means extending upwardly from the conveyor surface of said helical drying beds for dividing the said conveying surface into a plurality of separate conveying paths of different lengths.
 8. A freeze-drying apparatus comprising: a. a vacuum chamber; b. a drying bed arranged within the vacuum chamber having the shape of a helix disposed about a vertical axis; c. means for supplying frozen particles to one end of the drying bed; d. means for moving the frozen particles along the drying bed; e. means on each side of the drying bed for retaining the particles on the bed while they are being moved; f. means for heating the frozen particles while they are being moved along the bed; and g. means for removing the particles from the other end of the drying bed. 